CSS

It's high time we added some CSS styles to our HTML markup.
We'll not deep-dive into the details about the styles itself, as this is not a tutorial on Web Design.
The stylesheet can be downloaded from here in its final shape.
Place the Site.css stylesheet in the root directory of the project, and manually add following to the SuaveMusicStore.fsproj, inside <ItemGroup> element:

A browser, when asked to include a CSS file, sends back a request to the server with the given url.
In similar fashion, when the browser wants to render an image asset, it needs to GET it from the server.

If we have a look at our main WebPart we'll notice that there's really no handler capable of serving this file.
That's why we need to add another alternative to our chooseWebPart:

App.fs

23:

pathRegex"(.*)\.(css|png)">=>Files.browseHome

The pathRegexWebPart returns Some if an incoming request specifies path matching the regular expression pattern.
If that's the case, the Files.browseHome WebPart will be applied.
The given pattern matches every file with either .css or .png extension, which protects us from accessing other (e.g. binary or config) files.
Files.browseHome is a WebPart from Suave that serves static files from the root application directory.